Add support for editorconfig-checker

**Name:** editorconfig-checker
**URL:** https://github.com/editorconfig-checker/editorconfig-checker

From their repo:

> This is a tool to check if your files consider your .editorconfig-rules. Most tools - like linters for example - only test one filetype and need an extra configuration. This tool only needs your .editorconfig to check all files.
>
> Currently implemented editorconfig features are:
>
> * end_of_line
> * insert_final_newline
> * trim_trailing_whitespace
> * indent_style
> * indent_size
> * max_line_length